Metabolic syndrome (MteS) is comprised of a cluster of glucose intolerance, hypertension, and dyslipidemia with abdominal adiposity. It is a well-known predisposing factor for insulin resistance, diabetes mellitus, and cardiovascular diseases and is rising rapidly worldwide particularly in Western and Asian countries [10]. A recent meta-analysis reported increased (approximately 4-fold) risk of MteS after GDM especially in Caucasian and obese mothers[20].
The present study compared the delivery and postpartum outcomes of GDM between ART and spontaneous pregnancies, with regard to early MteS and glucose intolerance and their components. Our results showed a higher prevalence of MteS according to the NCEP criteria in the ART-GDM (20.8%) compared to the SC-GDM (10.9%) group. The prevalence of MteS was 19.4% in the GDM-ART and 17.2% in the SC-GDM based on the IDF criteria. Moreover, there was an 88% increase in the risk of developing MteS following ART pregnancy; nevertheless, in our study, the overall differences between the two groups were not statistically significant. Numerous studies have demonstrated higher rates of postpartum MteS in GDM women compared to control group within 1–11 years postpartum, with large variations according to the length of follow- up (7.5–60% in GDM and 4.6–26% in non-GDM women)[2]. However, few investigations have reported MteS at 6–12 weeks after gestational diabetes and there is no evidence in GDM following assisted conception. Recently, Nouhjah et al. observed that the frequency of early postpartum MteS was 18.2% in women with GDM and 11.6% in controls by the NCEP criteria, and 21% in women with gestational diabetes and 15.1% in controls by the IDF criteria [2].
Current findings showed that the incidence of postpartum glucose abnormalities included pre-diabetes (23 vs. 17.2%) and diabetes (3.3 vs. 3.1%) was not significantly different between GDM after ART and spontaneous conception. In a recent meta-analysis, the prevalence of pre-diabetes and diabetes was respectively 3.9–50.9% and 2.8–58% in Asian women with gestational diabetes within 4 weeks to 15 years postpartum based on the length of follow-up [21]. Considerable evidences propose that beta-cell dysfunction likely contributes to increase the risk of glucose intolerance in the first year postpartum in GDM women [22–24].
On the basis of our data, in univariate analyses, FBS, HbA1c, family history of diabetes in first relatives, and prior GDM were risk factors for postpartum glucose intolerance in GDM population. Furthermore, pre-pregnancy BMI, and second trimester levels of FBS, insulin, HDL and insulin resistance, were risk factors for postpartum MteS in GDM population. Multivariate analyses confirmed family history of diabetes as an independent predictor of both glucose intolerance and MteS 6 to 12 weeks postpartum, in GDM population. Additionally, second trimester FBS was another predictive factor of glucose intolerance 6–12 weeks after delivery. Numerous researches indicate several putative factors for postpartum glucose intolerance including family history of diabetes, elevated glucose level 120 min after a 75-g OGTT, elevated HbA1c levels during GDM diagnosis, perinatal complications, history of GDM, obesity, systolic or diastolic blood pressure, maternal age, parity, and insulin or metformin therapy [25–29]. Additionally, history of GDM, pre-pregnancy overweight or obesity, pregnancy systolic blood pressure, or requiring insulin or metformin were reported as predisposing factors that predict postpartum MteS in GDM population [2, 20].
Though, there were no significant differences in baseline characteristics such as mean maternal age, pre-pregnancy BMI, systolic and diastolic BP between the two groups, interestingly, our findings demonstrated that mean postpartum BMI and systolic blood pressure were significantly higher in the ART-GDM group. In addition, higher second trimester insulin and insulin resistance
Several investigations have reported increased blood pressure, dyslipidemia, and higher fasting glucose levels in ART-conceived children [30–32]. The current study showed the impact of mode of conception on delivery and postpartum outcomes of GDM pregnancies especially in mothers. The pathophysiological mechanisms underlying the MteS are on debate, but insulin resistance and visceral obesity are considered major causes. The presence of at least three of five criteria of MteS is link to an increased risk of heart disease, stroke, and diabetes.
However, it is not clear that whether early postpartum raised BMI and BP on future MteS in ART mothers. Moreover, ART mothers were suffering from anxiety and stress, hormonal and environmental alternations, ex vivo manipulations, inflammatory changes, endothelial dysfunction, metabolic disturbance and medical procedures during their pregnancies [33, 34]. These conditions may influence long-term women’s health and predispose occurrence of MteS and its components.
By the way, our study has several limitations needed to be addressed. First, this study lacks information regarding subfertility and infertility treatments during pregnancy. Second, we did not evaluate postpartum MteS and glucose intolerance in general population. Further prospective studies with larger sample size, particularly with inclusion a new group (natural pregnancy without GDM) and long-term follow up are required to verify our results.